These study guidelines are intended to describe a collaborative international study in APL in children and adolescents and to provide information about procedures for the entry, treatment and follow-up of patients. It is not intended that these guidelines be used as an aide-memoir or guide for the treatment of other patients. Every care has been taken in its drafting, but corrections and amendments may be necessary. Before entering patients into the study, clinicians must ensure that the study has received clearance from their Local Research Ethics Committee and any other necessary body.